;-----------------------------------------------------------------
; primfak.pro
;
; written by Andreas Reigber
;------------------------------------------------------------------
; calculates the primefactors of a number.
; I used this to estimate the time of a FFT (proportional to
; the sum of the primefactors of the array length).
;------------------------------------------------------------------
; This software has been released under the terms of the GNU Public
; license. See http://www.gnu.org/copyleft/gpl.html for details.
;------------------------------------------------------------------

pro primfak,zzz
   zahl=zzz   
   dif = 2.0
   sum = 0
   print,format='(A,$)',strcompress(zahl)
   print,format='(A,$)',' = '
loop:
   test = zahl/dif
   if fix(test)-test eq 0 then begin
       print,format='(A,$)',strcompress(fix(dif))
       sum=sum + dif
       zahl=zahl/dif
       if zahl ne 1 then print,format='(A,$)',' *'  
   endif else dif = dif + 1
   if zahl eq 1 then begin
       print,''
       print,'FFT Dauer ca.',strcompress(zzz*floor(sum))
       return
    endif
   goto,loop 

end